I met with an Accident on in 2008 (Almost 5 years back), and underwent ACL surgery
for my Right leg ligament tear in the same year.

The following conditions are the summary so far:

I never had swelling so far,
I am able to walk any long distance,
I do yoga moderately and routinley in the morning ,

I can also take stairs, but, if i take stairs continously for few days, i feel pain.

while resting, if i float my Right leg for longer period i feel pain, i mean that my leg should be grounded.

I also do not run or jog for long, this also will lead to pain.

The following are the issues :
1)
During night while i am asleep, sometimes i bend my Right leg too much, which causes pain.
Can i wear a belt or similar object on my right knee to avoid bending while i am asleep?

2) when i try to woke up in the morning, i feel pain for sometime and then it gradually reduces as i walk
why does this happen? what can i do to avoid this?

3) also, since last week i feel pain in the bottom part of my Right Knee
what can i do to avoid this?

4) whenever there is pain in my Right leg due to any of the above mentioned causes, it gradually diminishes over the days, and the time it takes depends on the nature of pain i had.

With these symptoms what is the overall picture?
What should i do to improve?

After ACL reconstruction some of pain is normal after prolonged activities or resting period. You can fight with this pain by a good physiotherapy session and regular strength ening exercises of knee muscles and ligaments.

Belt is not required to prevent bending of knee. You can use pillow underneath knee so that excessive bending can be prevented during sleeping.

Pain after you woke up in morning is due to some stiffness occurs to your replaced ligament and muscle around knee. This is the reason , it reduces gradually as you walk (ligament softens).

I advice you to do regular quadriceps and hamstring exercises. Your pain will definetly reduces as your knee getting stronger.